254 A. M. Mayer—History of Young's 
retina cannot distinguish between the white which is pro- 
duced by the union of scarlet and bluish-green light, and 
that which is composed of yellowish-green and violet, or of 
yellow and ultramarine blue, or of red, green and violet, or of 
all the colors of the spectrum united. All these combinations 
appear identically as white; and yet from «a physical point of 
view they are very different. In fact, the only resemblance be- 
tween the several combinations just mentioned is, that they are 
indistinguishable to the human eye. For instance, a surface 
illuminated with red and bluish-green light would come out 
black in a photograph; while another lighted with yellowish- 
green and violet would appear very bright, although both sur- 
faces alike seem to the eye to be simply white. 
* * * “Other colors, also, especially when they are not 
strongly pronounced, may, like pure white light, be composed 
of very different mixtures, and yet appear indistinguishable to 
the eye, while in every other property, physical or chemical, 
they are entirely distinct. 
* * * The theory of colors, with all these marvelous 
and complicated relations, was a riddle which Goethe in vain 
attempted to solve; nor were we physicists and physiologists 
more successful. I include myself in the number; for I long 
toiled at the task, without getting any nearer my object, until 
I at last discovered that a wonderfully simple solution had been 
discovered at the beginning of this century, and had been in 
print ever since for any one to read who chose. This solution 
was found and published by the same Thomas Young who first 
showed the right method of arriving at the interpretation of 
Egyptian hieroglyphics. He was one of the most acute men 
who ever lived, but had the misfortune to be too far in advance 
of his contemporaries. They looked on him with astonishment, 
